Electrosurgical Hyperthermia of Tissue and Laparoscopic Product Realization
Sellers, Orlando, Jr
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Permalink
https://hdl.handle.net/2142/83952
Description
Title
Electrosurgical Hyperthermia of Tissue and Laparoscopic Product Realization
Author(s)
Sellers, Orlando, Jr
Issue Date
1997
Doctoral Committee Chair(s)
Mike Philpott
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Medicine and Surgery
Language
eng
Abstract
This dissertation presents the results of work done to study the effect of radiofrequency hyperthermia on maximizing the electrosurgical tissue necrosis lesion volume and the development of a laparoscopic device based on these results. A theoretical model was derived which shows that the tissue's electrical conductivity has a greater effect on lesion formation than its thermal conductivity. This was characterized by deriving a nondimensional number, termed the W$\rm\sb{oc}$ number, as a function of the temperature change, thermal conductivity, electrical conductivity, and voltage. Results from the model were used to predict lesion size by determining the isopotential field from the application of RF energy to the tissue. The study showed that increasing the surface area of the electrode and electrode spacing, and minimizing the power level maximizes the tissue necrosis volume and minimizes the time to reach complete necrosis of the tissue. Further experiments demonstrated that the impedance rises exponentially at the end of the necrosis cycle while forming a resistive wall that impedes lesion growth called the Heat & Impedance Zone (HAIZ). There is a significant thermal and electrical impedance change in the HAIZ of the tissue that increases until an insulating layer forms. This layer grows until no further necrosis volume growth occurs. After that time, if the electrodes remain activated there is only charring of the tissue and coagulum adherence to the electrode. Lastly, information is presented on the development of several laparoscopic devices that are patent pending and in patent review.
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